1. Field of the Invention
The present invention relates to flexible lustrously metallized resinous articles and a process for manufacturing same. More particularly, the present invention relates to flexible lustrously metallized resinous molded articles comprised of thermoplastic resinous moldings as a substrate overlaid with a base coat, a metal film and a protective top coat in that order as well as a process for the manufacture of such flexible lustrously metallized resinous molded articles wherein a flexible resinous molded article is overlaid successively with a base coat, a metal film and a protective top coat by methods known per se.
2. Description of the Prior Art
The most generic method for furnishing resinous articles with metallic feeling and appearance is to form a metal film on the surface of the resinous articles. Heretofore, various methods have been proposed for the formation of a metal film on plastic products. Among these methods, a metal-painting method, a wet plating method, a hot-stamping method, a vacuum metallizing (metal vapor deposition) method, a sputtering method and the like ion-plating method have been used.
In recent years, flexible resinous products tend to be used in place of metallic products for bumper, front grill, head lamp housing and the like structures of motor vehicles according to the enforcement of the safety regulation for protuberant structures and for the purpose of weight-saving. In addition, a great demand exists in metallizing these flexible resinous products for improving their ornamental or aesthetic value in appearance.
On the other hand, however, resinous products metallized according to known conventional methods are limited only to those made of rigid resins such as ABS resin. No successful example has been reported hitherto on the satisfactory metallizing treatment for flexible resinous products.
A wet plating method which is one of the most popular methods for metallizing resinous products comprises applying a chemical metal-plating treatment onto the surface of the resinous products and then applying an electroplating treatment of a desired metal such as copper, nickel and chromium onto the chemically plated metal surface. The metal film formed on the surface of resinous products by such plating treatments has a thickness from several microns to several ten microns and spoils the soft flexible feeling of the resinous products because of poor malleability and ductility of such a relatively thick metal film. In a method for applying a metal-containing paint, the formed coating film exhibits good adhesion to the resinous products as substrate but the metal normally used in finely divided form in the paint fails to furnish the resinous products with a true metallic feeling. In case of a hot-stamping method wherein a metal foil used is satisfactorily thin, the soft flexible feeling of the products is not spoiled. However, this method has such a shortcoming that elongation of the metal foil is so small such that cracks are formed in the metal foil by deformation of the flexible resin.
A vacuum metallizing method or a sputtering method which has been increasingly popularized in recent years for furnishing resinous products with a metallic luster usually comprises applying a base coat onto the surface of a molded resinous article, forming a thin metal film by vapor deposition or sputtering on the surface of the base coat after its curing, and then applying a top coat serving as a protective layer onto the metal film. However, metallization of flexible resinous molded articles according to such a method for furnishing them with good metallic luster still has the disadvantage that the base coat used in such a method which must exhibit good adhesion to both of the flexible resin substrate and the metal film is poor in elongation (only 20-30%) one of the important characteristics required for the base coat, so that the base coat carrying the metal film tends to form cracks and is delaminated in the extreme case when the flexible resin substrate is subjected to deformation.
Accordingly, there is a great demand for developing an improved method for furnishing flexible resinous molded articles with a metallic luster, especially according to the vacuum deposition or sputtering method, without any problem developing of cracks or delamination in the metal film-carrying coat.